This is what I did.They were sealed when you put them away? I have a hard time with the attachment sometimes and found that if I put two lids on and then the attachment it vacuums better and then the extra lid just comes off with the attachment. I have not had one loose vacuum once I had it sealed tho. I wonder if you might have gotten a bit of flour on the rim and it caused it to lose seal due to the flour and rubber not making the best seal so that it looked sealed but slowly lost vacuum, I seal mainly my herbs and spices so haven't tried doing my flours yet. I just put them in the big buckets and freeze them for a week or so and then just store them. But I probably should vac-pack a few 5 or 10 pound bags for back storage.